As a resistance change type element that stores data utilizing a change in the resistance of the element, a Magnetic Random Access Memory (MRAM) has been developed. MRAM writing schemes include a magnetic field writing scheme and a spin injection writing scheme. In the magnetic field writing scheme, if the size of an MTJ (Magnetic Tunnel Junction) element is reduced, then holding power increases and thus there is a tendency of an increase in write current. On the other hand, in the spin injection writing scheme, since a Spin Transfer Torque (STT) writing scheme is used, the scheme has a characteristic that the smaller the size of a magnetic material, the lower the spin injection current required for magnetization reversal. Hence, an MTJ element of the spin injection writing scheme is advantageous in terms of achieving high integration, low power consumption, and high performance. In addition, although in the magnetic field writing scheme, erroneous writing to a non-selected memory cell may occur due to the spread of a magnetic field, in the spin injection writing scheme, such erroneous writing to a non-selected memory cell does not occur.
To achieve a fine MRAM, there is a need to adopt a spin injection type and promote the achievement of a finer MTJ element. However, to achieve a fine MTJ element, an MTJ film itself needs to be made thinner.
An MTJ element is formed in a manner such that a lower electrode layer, an MTJ film, an upper electrode layer, and a hard mask are deposited and are thereafter processed using lithographic and etching techniques. After processing the lower electrode layer, the MTJ film, and the upper electrode layer, a material of an interlayer dielectric film is deposited on the MTJ element. The interlayer dielectric film is etched back using a technique such as CMP (Chemical Mechanical Polishing) or dry etching, until a top surface of an upper electrode is exposed. Thereafter, a wiring line is formed on the upper electrode.
Since the interlayer dielectric film is etched back until the top surface of the upper electrode is exposed, the thinner the film thickness of the MTJ film, the thinner the film thickness of the interlayer dielectric film. When the interlayer dielectric film is too thin, there is a possibility that the wiring line connected to the upper electrode may be short-circuited to a lower electrode. In contrast, when the interlayer dielectric film is made sufficiently thick to prevent such a short-circuit, there is a possibility that the upper electrode may not be sufficiently exposed from the interlayer dielectric film, resulting in insufficient contact between the upper electrode and the wiring line. Namely, the promotion of the achievement of a fine MTJ element increases the possibility of the occurrence of a short-circuit between the upper electrode and the lower electrode or a contact failure between the upper electrode and the wiring line (e.g., a bit line).